CN116826315A

CN116826315A - Separator, preparation method thereof, battery and electric equipment

Info

Publication number: CN116826315A
Application number: CN202311095832.1A
Authority: CN
Inventors: 吴凯; 张楠楠; 景二东; 魏康景; 董康宇; 谢浩添; 孙信; 陈晓
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-08-29
Filing date: 2023-08-29
Publication date: 2023-09-29
Anticipated expiration: 2043-08-29
Also published as: CN116826315B

Abstract

The application discloses a separation membrane, a preparation method thereof, a battery and electric equipment. The isolating film comprises a first film layer, the first film layer comprises a first polymer and a capacity compensator, the capacity compensator comprises a lithium supplementing agent and/or a sodium supplementing agent, the lithium supplementing agent comprises lithium-containing metal oxide, and the sodium supplementing agent comprises Na ₂ O、Na ₂ O ₂ Or Na (or) ₂ CO ₃ At least one of (a) and (b); the second film layer is arranged on one side of the first film layer and comprises a second polymer and nano-filler. Therefore, the capacity compensator can release active lithium, the initial effect of the battery is improved, the nano filler can adsorb oxygen released by the capacity compensator in situ, the risk of explosion caused by mixing of the oxygen and the reducing gas is reduced, and the service life of the battery containing the isolating film is prolonged.

Description

Separator, preparation method thereof, battery and electric equipment

Technical Field

The application relates to the field of batteries, in particular to a separation film, a preparation method thereof, a battery and electric equipment.

Background

The battery is not only applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles, and the like, as well as a plurality of fields such as military equipment, aerospace, and the like. The battery can form a solid electrolyte membrane (SEI film) in the formation process, active metal ions can be consumed in the process of forming the SEI film, and in order to compensate irreversible capacity loss caused by forming the SEI film, a capacity compensation material is arranged on the positive electrode plate, and enough active metal ions can be released in the capacity compensation process in the first-week charging process, so that the first effect of the battery is improved. But oxygen can be released in the process of supplementing active metal ions by the capacity supplementing material, and the risk of explosion exists when the oxygen is mixed with the reducing gas, so that the service life of the battery is reduced.

Disclosure of Invention

In view of the technical problems in the background art, the application provides the isolating membrane, which can reduce the risk of explosion caused by mixing of oxygen released by a capacity compensator and reducing gas and improve the service life of a battery containing the isolating membrane.

A first aspect of the present application provides a separatorComprises a first film layer, wherein the first film layer comprises a first polymer and a capacity compensator, the capacity compensator comprises a lithium supplementing agent and/or a sodium supplementing agent, the lithium supplementing agent comprises lithium-containing metal oxide, and the sodium supplementing agent comprises Na ₂ O、Na ₂ O ₂ Or Na (or) ₂ CO ₃ At least one of (a) and (b); the second film layer is arranged on one side of the first film layer and comprises a second polymer and nano-filler.

According to the isolating film disclosed by the application, the first film layer and the second film layer are bonded through the first polymer and the second polymer, and the capacity compensator of the first film layer can release active metal ions, so that the first effect of the battery is improved. The nano filler in the second film layer can adsorb oxygen released by the capacity compensator in situ, so that the risk of explosion caused by mixing of the oxygen and the reducing gas is reduced, and the service life of the battery containing the isolating film is prolonged. The nano filler can also enhance the binding force between the isolating membrane and the pole piece, increase the mechanical strength of the isolating membrane and reduce the probability of dendrite penetrating through the isolating membrane. Meanwhile, by arranging the capacity compensator on the isolating film, the risk of gel generation of the positive electrode slurry caused by the addition of the capacity compensator into the positive electrode slurry can be reduced, and the preparation efficiency of the pole piece is improved.

According to some embodiments of the application, the volume average particle diameter D of the nanofiller _v 50 is 5nm-50nm. Thereby, uniformity of the second film layer is improved.

According to some embodiments of the application, the nanofiller comprises 10% -30% by mass based on the total mass of the barrier film. Thereby, the adsorption capacity of the nano-filler to oxygen is improved.

According to some embodiments of the application, the nanofiller comprises at least one of aluminum oxide, silicon dioxide, a metal organic framework-like compound, or a prussian blue analog. Therefore, the nano filler can adsorb oxygen, reduce the risk of explosion caused by mixing the oxygen with the reducing gas, and prolong the service life of the battery.

According to some embodiments of the application, the particle size D of the volume compensator _v 50 is 50nm-4 μm. Thereby improving the uniformity of the first film layer and the active goldBelongs to the compensation efficiency of ions.

According to some embodiments of the application, the volume compensator comprises 1.5% -10% by mass based on the total mass of the separator. Therefore, the capacity compensation agent improves the capacity of compensating active metal ions, improves the initial effect of the battery, reduces the brittleness of the isolating film, and reduces the risk of internal short circuit of the battery caused by the breakage of the isolating film.

According to some embodiments of the application, the separator has a porosity of 30% -70%. Thereby, ion transport efficiency is improved and internal resistance of the battery is reduced.

According to some embodiments of the application, the thickness of the first film layer is greater than the thickness of the second film layer. Therefore, the content of the capacity compensator is increased, the compensation effect of active metal ions is improved, and the first effect of the battery is improved.

According to some embodiments of the application, the first film layer has a thickness of 5 μm to 30 μm. Thereby, the effect of compensating the active metal ions of the first film layer is improved.

According to some embodiments of the application, the second film layer has a thickness of 3 μm to 15 μm. Therefore, the adsorption capacity of the nano filler to oxygen is improved, the risk of explosion caused by mixing of oxygen and reducing gas is reduced, and the service life of the battery is prolonged.

According to some embodiments of the application, at least a portion of the surface of the volume compensator is formed with a carbon coating. Thereby, the conductivity of the capacity compensator is improved.

According to some embodiments of the application, the carbon coating layer comprises 2% -10% by mass based on the total mass of the volume compensator. Thereby, the conductivity of the capacity compensator is improved, and at the same time, the ion transport rate of the first film layer is improved.

According to some embodiments of the application, the separator further comprises: the base film is arranged on one side, far away from the first film layer, of the second film layer; or the base film is arranged between the first film layer and the second film layer. Thus, the brittleness of the isolating film is reduced, and the mechanical strength of the isolating film is improved.

According to some embodiments of the application, the base film comprises a third polymer, the first polymer, the second polymer, and the third polymer each independently comprising at least one of a polyolefin-based polymer, a polynitrile-based polymer, or a polycarboxylate-based polymer.

The second aspect of the present application provides a method for producing a separator, comprising: applying a first slurry comprising a first polymer, a volume compensator, and a first solvent onto a support to form a first film layer; a second slurry comprising a second polymer, nanofiller, and a second solvent is applied to a side of the first film layer remote from the carrier to form a second film layer. Therefore, the isolating film with the capacity compensator and the nano filler is formed, the first effect of the battery is improved, the nano filler can absorb oxygen released by the capacity compensator in situ, the risk of explosion caused by mixing of the oxygen and the reducing gas is reduced, and the service life of the battery containing the isolating film is prolonged.

According to some embodiments of the application, the method further comprises: applying the first slurry to one side of a base film to form the first film layer, and applying the second slurry to the other side of the base film to form the second film layer; or applying the second slurry to a side of a base film to form the second film layer, and applying the first slurry to a side of the second film layer away from the base film to form the first film layer. Therefore, the base film is included in the isolating film, so that the mechanical strength of the isolating film can be improved, and meanwhile, the first film layer is located on one side, far away from the base film, of the second film layer, so that the lithium supplementing effect can be improved, and the first effect of the battery is improved.

According to some embodiments of the application, the nanofiller has a BET specific surface area of 200m ² /g-1500m ² And/g. Therefore, the adsorption effect of the nano filler on oxygen is improved, the risk of explosion caused by mixing of oxygen and reducing gas is reduced, and the service life of the battery is prolonged.

According to some embodiments of the application, the nanofiller has a porosity of 85% to 95%. Therefore, the adsorption quantity of the nano filler to oxygen is improved, the risk of explosion caused by mixing of oxygen and reducing gas is reduced, and the service life of the battery is prolonged. Meanwhile, the high porosity can enable oxygen to be quickly adsorbed by the nano-filler.

A third aspect of the present application provides a battery comprising the separator provided in the first aspect of the present application or the separator prepared by the method provided in the second aspect of the present application. Thereby, the life of the battery is improved.

According to some embodiments of the application, the battery further comprises: the positive pole piece and the negative pole piece, the barrier film is located between the positive pole piece and the negative pole piece, the first rete is close to the positive pole piece, the second rete is close to the negative pole piece. Therefore, the lithium supplementing efficiency of the capacity compensator of the first film layer is improved, after the capacity compensator releases oxygen, the oxygen is easy to move to the negative electrode side due to the high oxygen concentration at the positive electrode side and low oxygen concentration at the negative electrode side, the nano filler is close to the negative electrode side, the adsorption effect of the nano filler on the oxygen can be improved, the risk of explosion caused by mixing of the oxygen and the reducing gas is reduced, and the service life of the battery is prolonged.

A fourth aspect of the application provides a powered device comprising a battery provided in the third aspect of the application.

Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the application. Also, like reference numerals are used to designate like parts throughout the accompanying drawings. In the drawings:

FIG. 1 is a schematic view of a separator according to an embodiment of the present application;

FIG. 2 is a schematic structural view of a separator according to another embodiment of the present application;

FIG. 3 is a schematic view showing the structure of a separator according to another embodiment of the present application;

fig. 4 is a schematic view of the structure of a battery according to an embodiment of the present application;

fig. 5 is a schematic view of the structure of a battery module according to an embodiment of the present application;

fig. 6 is a schematic view of a structure of a battery pack according to an embodiment of the present application;

FIG. 7 is an exploded view of FIG. 6;

fig. 8 is a schematic diagram of an embodiment of a powered device with a battery as a power source.

Reference numerals illustrate:

10: a separation film; 100: a base film; 200: a second film layer; 300: a first film layer; 1: a battery; 2: a battery module; 3: a battery pack; 4: an upper case; 5: and a lower box body.

Detailed Description

Embodiments of the technical scheme of the present application are described in detail below. The following examples are only for more clearly illustrating the technical aspects of the present application, and thus are merely examples, and are not intended to limit the scope of the present application.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.

For simplicity, only a few numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form a range not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each separately disclosed point or individual value may itself be combined as a lower limit or upper limit with any other point or individual value or with other lower limit or upper limit to form a range not explicitly recited.

In the description of the embodiments of the present application, the term "and/or" is merely an association relationship describing an association object, and indicates that three relationships may exist, for example, a and/or B may indicate: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having" and any variations thereof in the description of the application and the claims and the description of the drawings above are intended to cover a non-exclusive inclusion.

Currently, the more widely the battery is used in view of the development of market situation. The battery is not only applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles, and the like, as well as a plurality of fields such as military equipment, aerospace, and the like. With the continuous expansion of the battery application field, the market demand thereof is also continuously expanding.

In the formation process of the battery, an SEI film can be formed on the surface of the negative electrode, a large amount of active metal ions can be consumed in the formation process of the SEI film, and the initial effect of the battery is reduced. In order to improve the initial efficiency of the battery, capacity compensation may be performed in advance for the negative electrode or the positive electrode. When the positive electrode is subjected to capacity compensation, an additive rich in active metal ions is generally adopted, a capacity compensation layer is established on the positive electrode plate, enough active metal ions are released in the first-week charge and discharge process, and irreversible capacity loss caused by SEI film generation is compensated. However, the capacity compensator releases oxygen after removing active metal ions, so that the electrolyte is oxidized to generate byproducts, the byproducts are diffused to the negative electrode to be reduced to generate hydrogen, and the reducing gas and the oxygen are mixed to have the risk of explosion.

According to the isolating film provided by the application, the capacity compensator and the nano filler are arranged on the isolating film, and the capacity compensator can release enough active metal ions, so that irreversible capacity loss caused by formation of the SEI film is compensated, and the initial efficiency of the battery is improved. Because the capacity compensator and the nano-filler are arranged on the isolating film, oxygen released in the lithium supplementing process of the capacity compensator can be adsorbed by the nano-filler in situ, the probability that the oxygen diffuses to the negative electrode to reduce and generate hydrogen is reduced, the risk of explosion caused by mixing the oxygen with the reducing gas is reduced, and the service life of the battery is prolonged. Meanwhile, as the capacity compensator is arranged on the isolating film, the risk that the capacity compensator is added into the positive electrode slurry to cause the positive electrode slurry to gel can be reduced, and the preparation rate of the pole piece can be improved.

A first aspect of the present application provides a separator 10, referring to fig. 1, the separator 10 includes a first film 300, the first film 300 including a first polymer and a capacity compensator including a lithium-supplementing agent including a lithium-containing metal oxide and/or a sodium-supplementing agent including Na ₂ O、Na ₂ O ₂ Or Na (or) ₂ CO ₃ At least one of (a) and (b); and a second film layer 200, the second film layer 200 being disposed on one side of the first film layer 300, the second film layer 200 including a second polymer and a nanofiller.

According to the isolating film 10 disclosed by the application, the first film layer 300 and the second film layer 200 are bonded through the first polymer and the second polymer, and the capacity compensator of the first film layer 300 can release active metal ions, so that the initial effect of the battery is improved. The nanofiller in the second membrane layer 200 can in situ adsorb oxygen released by the capacity compensator, reduce the risk of explosion caused by mixing oxygen with reducing gas, and improve the life of the battery containing the separator 10. The nano filler can also enhance the binding force between the isolating membrane 10 and the pole piece, increase the mechanical strength of the isolating membrane 10 and reduce the probability of dendrite penetrating the isolating membrane 10. The nanofiller may interact with the polar functional groups on the polymer to weaken the complexation of the active metal ions with the polar functional groups on the polymer and increase the conductivity of the barrier film 10 to the active metal ions. By providing the capacity compensator on the separator 10, the risk of gel generation of the positive electrode slurry due to the addition of the capacity compensator to the positive electrode slurry can be reduced, and the preparation efficiency of the pole piece can be improved.

According to some embodiments of the application, the volume average particle diameter D of the nanofiller _v 50 may be 5nm to 50nm, e.g. mayIn the range of 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, or the like, or may be any of the above numerical compositions. Therefore, the uniformity of the dispersion of the nano-filler in the second polymer is improved, the probability of agglomeration of the nano-filler in the second polymer is reduced, and the adsorption effect of the nano-filler on oxygen is further improved. According to some embodiments of the application, the nanofiller has a volume average particle diameter D _v 50 may be 20nm to 30nm.

In the application, D _v 50 is the particle size corresponding to a cumulative volume distribution percentage of 50%, and is measured by a laser particle size analyzer (Malvern Master Size 2000) with reference to, for example, standard GB/T19077-2016/ISO 13320:2009. The specific test process is as follows: taking a proper amount of a sample to be detected (the concentration of the sample is ensured to be 8% -12% of the shading degree), adding 20ml of deionized water, simultaneously carrying out ultrasonic treatment for 5min (53 KHz/120W) to ensure that the sample is completely dispersed, and then measuring the sample according to GB/T19077-2016/ISO 13320:2009 standard.

In the present application, the first polymer, the second polymer, the nanofiller and the capacity compensator may be separated by a melt process. Specifically, the melting point of the first polymer and the second polymer is about 200 ℃ to 300 ℃, the melting point of the nano-filler is greater than 2000 ℃, the melting point of the capacity compensator is about 600 ℃ to 1600 ℃, and the volume average particle size of the nano-filler is tested by heating and separating the isolating film and then adopting the method.

According to some embodiments of the present application, the nanofiller may be present in an amount of 10% -30%, for example, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28% or 30%, etc., or may be in a range of any of the above values based on the total mass of the separator 10. Therefore, by making the content of the nano-filler in the second film layer 200 in the above range, the adsorption amount of the nano-filler to oxygen is increased, the risk of explosion caused by mixing oxygen with the reducing gas is reduced, and the service life of the battery is prolonged. At the same time, the brittleness of the separator 10 is reduced, and the risk of short circuit inside the battery caused by breakage of the separator 10 is reduced. According to some embodiments of the present application, the nanofiller may be present in an amount of 15% -20% based on the total mass of the barrier film 10.

According to some embodiments of the application, the nanofiller may include at least one of aluminum oxide, silicon dioxide, a metal organic framework-based compound, or a prussian blue analog. Therefore, the nano filler can absorb oxygen released in the lithium supplementing process of the capacity compensator, reduce the risk of explosion caused by mixing of oxygen and reducing gas, and prolong the service life of the battery.

According to some embodiments of the application, the metal organic framework-based compound comprises M-MOF-74, wherein M comprises at least one of Mg, mn, fe, co, ni, cu or Zn. According to some embodiments of the application, M comprises at least one of Cu, zn or Mn.

According to some embodiments of the application, the prussian blue analog comprises MFe (CN) ₆ Wherein M comprises at least one of K, na, zn, fe, co, ni or Mn. According to some embodiments of the application, M comprises at least one of Zn, fe or Co.

According to some embodiments of the application, the volume average particle diameter D of the volume compensator _v 50 may be 50nm to 4 μm, for example, 50nm, 500nm, 1000nm, 1500nm, 2000nm, 2500nm, 3000nm, 3500nm or 4000nm, etc., or may be in the range of any of the above numerical compositions. Therefore, the uniformity of the dispersion of the capacity compensator in the first polymer is improved, the probability of agglomeration of the capacity compensator in the first polymer is reduced, the polarization degree of the active metal ion extraction reaction in the process of compensating the active metal ion by the capacity compensator is reduced, and the compensation efficiency of the active metal ion is improved. According to some embodiments of the application, the volume average particle diameter D of the volume compensator _v 50 may be 1 μm to 3 μm.

According to some embodiments of the present application, the mass ratio of the capacity compensator may be 1.5% -10%, for example, may be 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., or may be in the range of any of the above values, based on the total mass of the separator 10. Thus, by making the content of the capacity compensator within the above range, the capacity compensator can release sufficient active metal ions to enhance the initial efficiency of the battery. At the same time, the brittleness of the separator 10 can be reduced, and the risk of short circuit inside the battery caused by breakage of the separator 10 can be reduced. According to some embodiments of the present application, the volume compensator may have a mass ratio of 2% -7% based on the total mass of the separator 10.

According to some embodiments of the application, at least a portion of the surface of the volume compensator may be formed with a carbon coating. For example, a carbon coating layer may be formed on a part of the surface of the capacity compensator, or a carbon coating layer may be formed on both surfaces of the capacity compensator. Thereby, the conductivity of the capacity compensator is improved. Specifically, the carbon in the carbon coating layer may be amorphous carbon or graphitized carbon generated by the cracking of the carbon source.

According to some embodiments of the application, the carbon coating may have a mass fraction of 2% -10%, e.g., may be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10%, etc., or may be in the range of any of the above values, based on the total mass of the volume compensator. Thus, by setting the carbon content in the carbon coating layer to the above range, the ion conductivity of the first film 300 is improved while the conductivity of the capacity compensator is improved. According to some embodiments of the present application, the carbon coating may have a mass ratio of 4% -7% based on the total mass of the barrier film 10.

The method for testing the carbon content in the carbon coating comprises the following steps: weighing appropriate amount of supplement into crucible, adding appropriate amount of fluxing agent (pure iron fluxing agent, pure tin fluxing agent and pure tungsten fluxing agent), mixing, and burning sample in oxygen to convert carbon into CO ₂ After entering the absorption tank, the absorption liquid is converted into corresponding signals by the detector. The signal is sampled by a computer, converted into CO after linear correction ₂ And adding the values of the whole analysis process, dividing the added values by the weight value in a computer after the analysis is finished, multiplying the added values by a correction coefficient, and subtracting the blank to obtain the percentage of carbon in the sample.

According to some embodiments of the application, the volume compensation agent may include at least one of a lithium or sodium supplement. For example, when the battery is a lithium ion battery, the lithium supplementing agent can supplement active lithium in the battery formation process, so that the first effect of the battery is improved. When the battery is a sodium ion battery, the sodium supplementing agent can supplement active sodium, and the first effect of the battery is improved.

According to some embodiments of the application, the lithium supplement may include a lithium-containing metal oxide. Therefore, lithium ions can be released, active lithium consumption is supplemented, and the first effect of the battery is improved.

According to some embodiments of the application, the lithium-containing metal oxide comprises Li _x M ₁ O _0.5(2+x) 、Li ₂ M ₂ O ₃ 、Li ₂ M ₃ O ₄ 、Li ₃ M ₄ O ₄ 、Li ₅ M ₅ O ₄ Or Li (lithium) ₅ M ₆ O ₆ At least one of (1), wherein x is greater than or equal to 1, M ₁ Comprises at least one of Ni, co, fe, mn, zn, mg, ca, cu or Sn, M ₂ Comprises at least one of Ni, co, fe, mn, sn or Cr, M ₃ Comprises at least one of Ni, co, fe, mn, sn, cr, V or Nb, M ₄ Comprises at least one of Ni, co, fe, mn, sn, cr, V, mo or Nb, M ₅ Comprises at least one of Ni, co, fe, mn, sn, cr or Mo, M ₆ Comprises at least one of Ni, co or Mn, M ₁ 、M ₂ 、M ₃ 、M ₄ 、M ₅ 、M ₆ The valence state of each element is respectively lower than the highest oxidation valence state of the element.

According to some embodiments of the application, the sodium supplement may include Na ₂ O、Na ₂ O ₂ Or Na (or) ₂ CO ₃ At least one of them.

According to some embodiments of the present application, the porosity of the separator 10 may be 30% -70%, for example, 30%, 40%, 50%, 60% or 70%, etc., or may be in the range of any of the above values. By this, the porosity of the separator 10 is set within the above range, and thus the ion transport capacity of the separator 10 is improved. According to some embodiments of the application, the porosity of the barrier film 10 is 40% -50%.

The method for testing the porosity of the isolating film comprises the following steps: kneading the isolating film into a block, filling the block into a sample cup, placing the sample cup filled with the sample into a true density tester, sealing a testing system, introducing helium gas according to a program, detecting the gas pressure in a sample chamber and an expansion chamber, and calculating the real volume according to Bohr's law (PV=nRT), thereby obtaining the porosity of the sample to be tested.

According to some embodiments of the application, the volume average particle diameter D is due to the volume compensator _v 50 is greater than the volume average particle diameter D of the nano-filler _v 50, the thickness of the first film 300 may be greater than the thickness of the second film 200. Therefore, the active metal ions released by the capacity compensator on the isolating membrane 10 can compensate the active metal ions lost in the battery formation process, and the initial efficiency of the battery is improved; the nano filler on the isolating film 10 fully absorbs the oxygen released by the capacity compensator, reduces the risk of explosion caused by mixing the oxygen with the reducing gas, and prolongs the service life of the battery.

The thickness test method in the application comprises the following steps: the uniform and flat isolating film is placed between the measuring rod and the measuring meter of the spiral micrometer, the protecting knob is rotated until the measured object is clamped until the ratchet makes a sound, and the measuring rod is fixed by the fluctuation fixing knob to read. And 6 times of measurement are carried out at different positions, and the thickness of the isolating film is obtained by taking an average value.

According to some embodiments of the present application, when the thickness of the first film layer 300 is greater than the thickness of the second film layer 200, the thickness of the separation film 10 may be 10 μm to 45 μm, for example, may be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, or the like, or may be in a range of any of the numerical compositions described above. Thereby, the space occupied by the separator 10 is reduced, and the energy density of the battery is improved. According to some embodiments of the application, the thickness of the barrier film 10 may be 15 μm to 30 μm.

According to some embodiments of the present application, when the thickness of the first film layer 300 is greater than the thickness of the second film layer 200, the thickness of the first film layer 300 may be 5 μm to 30 μm, for example, may be 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or the like, or may be a range of any of the numerical compositions described above. Thus, by making the thickness of the first film 300 satisfy the above range, the content of the capacity compensator in the first film 300 can be increased, the compensation effect of the active metal ions can be improved, and the initial efficiency of the battery can be improved. According to some embodiments of the application, the first film 300 has a thickness of 10 μm to 20 μm.

According to some embodiments of the present application, when the thickness of the first film layer 300 is greater than the thickness of the second film layer 200, the thickness of the second film layer 200 may be 3 μm to 15 μm, for example, may be 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, or the like, or may be a range of any of the numerical compositions described above. Thus, by making the thickness of the second film layer 200 satisfy the above range, the content of the nanofiller in the second film layer 200 can be increased, the adsorption effect of the nanofiller on oxygen can be improved, the risk of explosion caused by mixing oxygen with the reducing gas can be reduced, and the life of the battery can be prolonged. According to some embodiments of the application, the thickness of the second film layer 200 may be 5 μm to 10 μm.

According to some embodiments of the present application, referring to fig. 2 and 3, the isolation diaphragm 10 may further include: a base film 100, wherein the base film 100 is disposed on a side of the second film layer 200 away from the first film layer 300; or the base film 100 is provided between the first film layer 300 and the second film layer 200. Thereby, the mechanical strength of the separator 10 is improved.

According to some embodiments of the present application, the thickness of the base film 100 may be 5 μm to 7 μm, for example, may be 5 μm, 5.4 μm, 5.8 μm, 6.2 μm, 6.6 μm, or 7 μm, etc., or may be in the range of any of the numerical compositions described above. Thus, by setting the thickness of the base film 100 in the above-described range, the mechanical strength of the separator 10 can be improved, the thickness of the separator 10 as a whole can be reduced, the space occupied by the separator 10 can be reduced, and the energy density of the battery can be improved.

According to some embodiments of the application, the porosity of the base film 100 may be 35% -40%, for example, 35%, 36%, 37%, 38%, 39% or 40%, etc., or may be in the range of any of the numerical compositions described above. This improves the ion transport efficiency of the base film 100 and reduces the internal resistance of the battery.

In the present application, the porosity test method of the base film 100 is as follows: the base film 100 was kneaded into a mass and packed into a sample cup, the sample cup with the sample was placed in a true density tester, a test system was closed, helium gas was programmed in, and the true volume was calculated according to bohr's law (pv=nrt) by detecting the gas pressure in the sample chamber and the expansion chamber, thereby obtaining the porosity of the base film 100.

According to some embodiments of the application, the first polymer may have a weight average molecular weight of 3 ten thousand to 10 ten thousand, for example, 3 ten thousand, 4 ten thousand, 5 ten thousand, 6 ten thousand, 7 ten thousand, 8 ten thousand, 9 ten thousand, 10 ten thousand, etc., or may have a range of any of the numerical compositions mentioned above. This increases the viscosity of the first polymer and improves the uniformity of the entire separator 10. According to some embodiments of the application, the first polymer may have a weight average molecular weight of 5 ten thousand to 7 ten thousand.

According to some embodiments of the application, the weight average molecular weight of the second polymer may be 3 ten thousand to 10 ten thousand, for example, may be 3 ten thousand, 4 ten thousand, 5 ten thousand, 6 ten thousand, 7 ten thousand, 8 ten thousand, 9 ten thousand, 10 ten thousand, etc., or may be a range of any of the numerical compositions mentioned above. This increases the viscosity of the second polymer and improves the uniformity of the entire separator 10. According to some embodiments of the application, the second polymer may have a weight average molecular weight of 5-7 tens of thousands.

According to some embodiments of the present application, the material of the base film 100 includes a third polymer, and the weight average molecular weight of the third polymer may be 3 ten thousand to 10 ten thousand, for example, may be 3 ten thousand, 4 ten thousand, 5 ten thousand, 6 ten thousand, 7 ten thousand, 8 ten thousand, 9 ten thousand, 10 ten thousand, etc., or may be a range of any of the numerical compositions mentioned above. This increases the viscosity of the third polymer and improves the uniformity of the entire separator 10. According to some embodiments of the application, the third polymer may have a weight average molecular weight of 5-7 tens of thousands.

The weight average molecular weights of the first polymer, the second polymer, and the third polymer may be the same or different. According to some embodiments of the present application, the weight average molecular weights of the first polymer, the second polymer, and the third polymer are the same, thereby further improving the uniformity of the separator 10 as a whole.

According to some embodiments of the application, the first polymer comprises at least one of a polyolefin-based polymer, a polynitrile-based polymer, or a polycarboxylate-based polymer. According to some embodiments of the application, the first polymer comprises at least one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylene carbonate, polycyanoacrylate, polymethacrylate, polyacrylonitrile, polymaleic anhydride, polyethylene, polypropylene, or polyvinylidene fluoride.

According to some embodiments of the application, the second polymer comprises at least one of a polyolefin-based polymer, a polynitrile-based polymer, or a polycarboxylate-based polymer. According to some embodiments of the application, the second polymer comprises at least one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylene carbonate, polycyanoacrylate, polymethacrylate, polyacrylonitrile, polymaleic anhydride, polyethylene, polypropylene, or polyvinylidene fluoride.

According to some embodiments of the application, the third polymer comprises at least one of a polyolefin-based polymer, a polynitrile-based polymer, or a polycarboxylate-based polymer. According to some embodiments of the application, the third polymer comprises at least one of polyvinylidene fluoride-hexafluoropropylene copolymer, polyvinylene carbonate, polycyanoacrylate, polymethacrylate, polyacrylonitrile, polymaleic anhydride, polyethylene, polypropylene, or polyvinylidene fluoride.

Thus, the first film 300, the second film 200 and the base film 100 are bonded by the first polymer, the second polymer and the third polymer to form the complete barrier film 10, thereby improving the uniformity of the barrier film 10 as a whole.

The first polymer, the second polymer, and the third polymer may be the same material or different materials. According to some embodiments of the application, the first polymer, the second polymer, and the third polymer are the same material.

The second aspect of the present application provides a method for producing a release film 10, comprising: applying a first slurry comprising a first polymer, a volume compensator, and a first solvent onto a support to form a first film 300; a second slurry comprising a second polymer, nanofiller, and a second solvent is applied to a side of the first film layer 300 remote from the carrier to form a second film layer 200. Specifically, after the first slurry is applied to the carrier, the carrier is dried to form a first film layer 300, the second slurry is applied to the side of the first film layer 300 away from the carrier, the second film layer 200 is dried to form a second film layer, and the carrier is peeled off to form the separator 10. Thus, the isolating film 10 with the capacity compensator and the nano filler is formed, the first effect of the battery is improved, the nano filler can absorb oxygen released by the capacity compensator in situ, the risk of explosion caused by mixing of the oxygen and the reducing gas is reduced, and the service life of the battery containing the isolating film 10 is prolonged.

According to some embodiments of the application, the method of applying the first and second slurries may include at least one of knife coating, electrospinning, or spray coating.

According to some embodiments of the application, the nanofiller may have a BET specific surface area of 200m ² /g-1500m ² /g, for example, may be 200m ² /g、400m ² /g、600m ² /g、800m ² /g、1000m ² /g、1200m ² /g、1400m ² /g or 1500m ² /g, etc., or may be in the range of any of the numerical compositions described above. Thus, the specific surface area of the nano-filler is larger, the adsorption amount of the nano-filler to oxygen can be increased while oxygen is adsorbed in situ, the risk of explosion caused by mixing of oxygen and reducing gas is reduced, and the service life of the battery containing the isolating membrane 10 is prolonged. According to some embodiments of the application, the nanofiller may have a BET specific surface area of 500m ² /g-1000m ² /g。

The specific surface area test method of the nano filler in the application comprises the following steps: about 7g of the sample is put into a 9cc long tube with a bulb by using a American microphone multi-station type full-automatic specific surface area and pore analyzer GeminiVII2390, deaerated for 2 hours at 200 ℃, and then put into a host machine for testing to obtain the specific surface area data of the nano-filler.

According to some embodiments of the application, the nanofiller may have a porosity of 85% -95%, for example, 85%, 87%, 89%, 91%, 93% or 95%, etc., or may be in the range of any of the values recited above. Therefore, after the capacity compensator releases oxygen, the nano filler has larger porosity, and the rate of adsorbing oxygen by the nano filler can be improved. When the nano filler has larger specific surface area and larger porosity, the nano filler can adsorb oxygen in situ, and simultaneously can improve the adsorption rate and adsorption quantity of oxygen, further reduce the risk of explosion caused by mixing oxygen with reducing gas, and improve the service life of the battery containing the isolating membrane 10. According to some embodiments of the application, the nanofiller may have a porosity of 90% to 95%.

The method for testing the porosity of the nano-filler comprises the following steps: placing a sample cup containing a sample in a true density tester, sealing a testing system, introducing helium gas according to a program, detecting the pressure of the gas in a sample chamber and an expansion chamber, and calculating the true volume according to Bohr's law (PV=nRT), thereby obtaining the porosity of the sample.

According to some embodiments of the present application, referring to fig. 2, when the base film 100 is included in the separation film 10 and the base film 100 is located between the first film layer 300 and the second film layer 200, the method of forming the first film layer 300 and the second film layer 200 further includes: the first paste is applied to one side of the base film 100 to form the first film layer 300, and the second paste is applied to the other side of the base film 100 to form the second film layer 200. Therefore, the carrier is not required in the preparation process of the isolating membrane 10, the isolating membrane 10 comprising the base membrane 100, the first membrane layer 300 and the second membrane layer 200 is directly formed, the mechanical strength of the isolating membrane 10 is improved, the preparation process of the isolating membrane 10 is simplified, and the production cost is reduced.

According to some embodiments of the present application, referring to fig. 3, when the base film 100 is included in the isolation film 10 and the second separator is located at one side of the base film 100 and the first separator is located at one side of the second separator remote from the base film 100, the method of forming the first film layer 300 and the second film layer 200 further includes: the second paste is applied to a side of the base film 100 to form the second film layer 200, and the first paste is applied to a side of the second film layer 200 remote from the base film 100 to form the first film layer 300. Therefore, the carrier is not required in the preparation process of the isolating membrane 10, the isolating membrane 10 comprising the base membrane 100, the first membrane layer 300 and the second membrane layer 200 is directly formed, the mechanical strength of the isolating membrane 10 is improved, the preparation process of the isolating membrane 10 is simplified, and the production cost is reduced.

According to some embodiments of the application, the slurry may be knife coated onto the carrier or base film 100 by a preparer.

According to some embodiments of the application, the viscosity of the first slurry may be 0.1Pa at 55deg.CS-10Pa/>S, for example, may be 0.1 Pa->S、1Pa/>S、2Pa/>S、3Pa/>S、4Pa/>S、5Pa/>S、6Pa/>S、7Pa/>S、8Pa/>S、9Pa/>S or 10 Pa->S, etc., or may be in the range of any of the numerical compositions described above. Thus, the fluidity of the first slurry is improved, the difficulty of film formation is reduced, and the uniformity of the first film 300 is improved. According to some embodiments of the application, the viscosity of the first paste is 5Pa +.>S-8Pa/>S。

In the present application, "viscosity" is in the sense known in the art and can be measured by means of instruments and methods known in the art, for example, reference being made to GB/T10247-1988.

According to some embodiments of the application, the second slurry may have a viscosity of 0.1Pa at 55deg.CS-10Pa/>S, for example, may be 0.1 Pa->S、1Pa/>S、2Pa/>S、3Pa/>S、4Pa/>S、5Pa/>S、6Pa/>S、7Pa/>S、8Pa/>S、9Pa/>S or 10 Pa->S, etc., or may be in the range of any of the numerical compositions described above. Thus, the fluidity of the second slurry is improved, the difficulty of film formation is reduced, and the uniformity of the second film layer 200 is improved. According to some embodiments of the application, the viscosity of the second paste may be 5Pa +. >S-8Pa/>S。

According to some embodiments of the application, the first solvent in the first slurry may include at least one of N, N-dimethylformamide, N-dimethylacetamide, acetone, N-methylpyrrolidone, hexafluoroisopropanol, or tetrahydrofuran.

According to some embodiments of the application, the second solvent in the second slurry may include at least one of N, N-dimethylformamide, N-dimethylacetamide, acetone, N-methylpyrrolidone, hexafluoroisopropanol, or tetrahydrofuran.

A third aspect of the present application provides a battery comprising the separator 10 provided in the first aspect of the present application or the separator 10 prepared by the method provided in the second aspect of the present application. Thereby, the life of the battery is improved.

According to some embodiments of the application, the battery further comprises: the isolating film 10 is positioned between the positive electrode plate and the negative electrode plate, the first film 300 is close to the positive electrode plate, and the second film 200 is close to the negative electrode plate. Therefore, the lithium supplementing efficiency of the capacity compensator of the first film 300 is improved, after the capacity compensator releases oxygen, the oxygen is easy to move to the negative electrode side due to the high oxygen concentration at the positive electrode side and low oxygen concentration at the negative electrode side, the nano filler is close to the negative electrode side, the adsorption effect of the nano filler on the oxygen can be improved, the risk of explosion caused by mixing the oxygen with the reducing gas is reduced, and the service life of the battery is prolonged.

[ Positive electrode sheet ]

The positive pole piece comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector, wherein the positive film layer comprises a positive active material.

As an example, the positive electrode current collector has two surfaces opposing in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two surfaces opposing the positive electrode current collector.

In some embodiments, the positive current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, when the battery is a lithium ion battery, the positive electrode active material may be a positive electrode active material for lithium ion batteries, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxide (e.g. LiNiO) ₂ ) Lithium manganese oxide (e.g. LiMnO ₂ 、LiMn ₂ O ₄ ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM) ₃₃₃ ）、LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also referred to as NCM) ₅₂₃ ）、LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also referred to as NCM) ₂₁₁ ）、LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also referred to as NCM) ₆₂₂ ）、LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM) ₈₁₁ ) Lithium nickel cobalt aluminum oxide (e.g. LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) And at least one of its modified compounds and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO ₄ (also abbreviated as LFP)), composite material of lithium iron phosphate and carbon, and manganese lithium phosphate (such as LiMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, and a composite material of lithium manganese phosphate and carbon.

In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and (3) coating the positive electrode slurry on a positive electrode current collector, and obtaining a positive electrode plate after the procedures of drying, cold pressing and the like.

[ negative electrode sheet ]

The negative electrode plate comprises a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode film layer comprises a negative electrode active material.

As an example, the anode current collector has two surfaces opposing in its own thickness direction, and the anode film layer is provided on either one or both of the two surfaces opposing the anode current collector.

In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

In some embodiments, the anode active material may employ an anode active material for a battery, which is well known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery anode active material may be used. These negative electrode active materials may be used alone or in combination of two or more.

In some embodiments, the negative electrode film layer further optionally includes a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the negative electrode film layer may optionally further include other adjuvants, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

In some embodiments, the negative electrode sheet may be prepared by: dispersing the above components for preparing the negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and obtaining a negative electrode plate after the procedures of drying, cold pressing and the like.

[ electrolyte ]

The electrolyte plays a role in ion conduction between the positive electrode plate and the negative electrode plate. The application is not particularly limited in the kind of electrolyte, and may be selected according to the need.

In some embodiments, the electrolyte is an electrolyte. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonyl imide, lithium bis-trifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium difluorodioxaato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl sulfone, and diethyl sulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives capable of improving certain properties of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, and the like.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator 10 may form an electrode assembly through a winding process or a lamination process. The electrode assembly is encapsulated in the accommodating cavity. The number of electrode assemblies included in the battery may include one or more and may be adjusted according to the need.

The shape of the battery according to the embodiment of the present application is not particularly limited, and may be cylindrical, square, or any other shape. Fig. 4 shows a square battery 1 as an example.

In some embodiments, the battery 1 may include an outer package. The outer package is used for packaging the positive electrode plate, the negative electrode plate and the electrolyte.

In some embodiments, the outer package may include a housing and a cover. Wherein, the casing can include the bottom plate and connect the curb plate on the bottom plate, and bottom plate and curb plate enclose and close and form the chamber that holds. The shell is provided with an opening communicated with the accommodating cavity, and the cover plate can be covered on the opening to seal the accommodating cavity.

In some embodiments, the exterior package of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell.

The outer package of the battery may also be a pouch, such as a pouch-type pouch. The soft bag can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

In some embodiments, the cells may be assembled into a battery module, and the number of cells contained in the battery module may be plural, with the specific number being adjustable according to the application and capacity of the battery module.

In some embodiments, the exterior packaging of the battery may include a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell.

Fig. 5 is a battery module 2 as an example. Referring to fig. 5, in the battery module 2, a plurality of batteries 1 may be sequentially arranged in the longitudinal direction of the battery module 2. Of course, the arrangement may be performed in any other way. The plurality of batteries 1 may be further fixed by fasteners.

The battery module 2 may further include a case having an accommodating space in which the plurality of batteries 1 are accommodated. In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.

Fig. 6 and 7 are diagrams of the battery pack 3 as an example. Referring to fig. 6 and 7, a battery case and a plurality of battery modules 2 disposed in the battery case may be included in the battery pack 3. The battery box includes an upper box body 4 and a lower box body 5, and the upper box body 4 can be covered on the lower box body 5 and forms a closed space for accommodating the battery module 2. The plurality of battery modules 2 may be arranged in the battery case in any manner.

A fourth aspect of the application provides a powered device comprising a battery according to the third aspect. Specifically, the battery can be used as a power supply of the electric equipment and also can be used as an energy storage unit of the electric equipment. The powered device may include, but is not limited to, mobile devices (e.g., cell phones, notebook computers), electric vehicles (e.g., electric only vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks), electric trains, watercraft and satellites, energy storage systems.

Fig. 8 is a powered device as an example. The electric equipment comprises a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle.

As another example, the powered device may include a cellular phone, a tablet computer, a notebook computer. The electric equipment is required to be light and thin, and a battery can be used as a power supply.

In order to make the technical problems, technical schemes and beneficial effects solved by the embodiments of the present application more clear, the following will be described in further detail with reference to the embodiments and the accompanying drawings. It will be apparent that the described embodiments are only some, but not all, embodiments of the application. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the application, its application, or uses. All other embodiments, which can be made by a person skilled in the art based on the embodiments of the application without any inventive effort, are intended to fall within the scope of the application.

Example 1

1. Preparation of a separator film

Polyacrylonitrile (PAN) and Li ₅ FeO ₄ Drying in an oven at 60deg.C for 12h, followed by dissolving 14.25g of PAN in 30 mL acetone solution, followed by 1.43g of Li ₅ FeO ₄ Adding the polymer into a polymer solution, stirring the polymer solution in an oil bath at 70 ℃ for 12h to prepare polymer slurry, scraping the polymer slurry on an aluminum foil by a preparation device, and drying the polymer slurry at 80 ℃ in vacuum for 24 h to remove an acetone solvent to obtain a first film layer with the thickness of 16 mu m;

the PAN and Mg-MOF-74 are placed in a 60 ℃ oven to be dried for 12 hours, 14.25g of PAN is dissolved in 30 mL acetone solution, 5.8g of Mg-MOF-74 is added into the polymer solution, the polymer slurry is prepared by stirring 12h in an oil bath at 70 ℃, the polymer slurry is scraped on a first film layer by a preparation device, the acetone solvent is removed by drying 24 h at 80 ℃ in vacuum, a second film layer with the thickness of 14 mu m is obtained, and the aluminum foil is peeled off, thus obtaining the isolating film.

2. Preparation of positive electrode sheet

LiFePO is prepared ₄ (LFP), conductive agent acetylene black and binder are fully stirred and mixed uniformly in N-methyl pyrrolidone solvent according to the weight ratio of 97:1:2, the volume average particle size of LFP particles is 1.2 mu m, coated on aluminum foil, dried and cold-pressed, and the positive plate is obtained.

3. Preparation of negative electrode sheet

The active material artificial graphite, the conductive agent acetylene black, the binder Styrene Butadiene Rubber (SBR) and the thickener sodium carboxymethyl cellulose (CMC-Na) are mixed according to the weight ratio of 96.5:0.7:1.8: and 1, fully stirring and uniformly mixing the materials in deionized water, coating the materials on a copper foil, drying and cold pressing the materials to obtain the negative electrode plate.

4. Preparation of electrolyte

Mixing Ethylene Carbonate (EC) and diethyl carbonate (DEC) in a mass ratio of 50/50, and dissolving 1.1mol of LiPF ₆ Lithium salt, liPF ₆ The concentration of the substance in the electrolyte was 1.1 mol/L.

5. Preparation of a cell

And sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, wherein a first film layer of the isolating film is close to the positive electrode plate, a second film layer of the isolating film is close to the negative electrode plate, the isolating film is positioned between the positive electrode plate and the negative electrode plate to play a role in isolation, and the bare cell is obtained by winding. And placing the bare cell in an outer package, injecting prepared basic electrolyte, and packaging.

The preparation methods of the batteries of example 2-example 54, comparative example 1 and comparative example 2 are the same as those of example 1, and the differences are shown in Table 1. Examples 52 and 53 include a base film between a first film layer and a second film layer, i.e., li-containing film ₅ FeO ₄ The polymer slurry containing Mg-MOF-74 is blade coated on the surface of the base film remote from the first film layer.

The composition of the separator in examples 48-51 was the same, and the separator was made to have different porosities by adjusting the drying temperature during the preparation of the separator. For example, the first and second film layers in example 48 were baked at 120 ℃, the first and second film layers in example 49 were baked at 105 ℃, the first and second film layers in example 50 were baked at 85 ℃, and the first and second film layers in example 51 were baked at 50 ℃.

TABLE 1

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The batteries in examples 1 to 54, comparative example 1 and comparative example 2 were subjected to a separator film thickness test, a specific discharge capacity test, a high-temperature storage performance test and a swelling degree test, and the test results are shown in table 2.

Performance testing

1. Isolation film thickness testing method

The uniform and flat isolating film is placed between the measuring rod and the measuring meter of the spiral micrometer, the protecting knob is rotated until the measured object is clamped until the ratchet makes a sound, and the measuring rod is fixed by the fluctuation fixing knob to read. And 6 times of measurement are carried out at different positions, and the thickness of the isolating film is obtained by taking an average value.

2. Discharge specific capacity test method

Constant-current discharge at 25 ℃ to discharge termination voltage at 0.33C rate, and the discharge capacity is Ed ₀ . Using Ed ₀ Divided by the mass of the positive electrode active material of the battery to obtain the specific discharge capacity. That is, specific discharge capacity (mAh/g) =1 st turn discharge capacity/positive electrode active material mass. The above test of specific discharge capacity was repeated 5 times, and the average value was the specific discharge capacity listed in table 2 below.

3. High temperature storage performance test for battery

Five cells were used for each example for parallel testing, each cell was charged at 25℃to a voltage of 3.65V at 1C, and then discharged at 1C to a voltage of 2.5V, and the reversible capacity was measured to be E ₀ . The fully charged battery was then placed in an oven at 60℃for 100 days, and after 100 days the battery was removed and immediately tested for reversible capacity and designated E _n . The capacity retention epsilon, epsilon= (E) of the battery after 100 days of storage at 60℃was calculated according to the following formula _n -E ₀ )/E ₀ ×100%。

4. Method for testing expansion degree of battery

The thickness d of each cell in the initial state was measured with a vernier caliper at 25 ℃ ₁ And a final state thickness d after 100 cycles of charging to a voltage equal to 3.65V at a rate of 1C and discharging to a voltage equal to 2.5V at a rate of 1C ₂ To calculate the swelling degree of the battery. The thickness of the cell increased after 100 cycles, d=d, was calculated according to the following formula ₂ -d ₁ 。

5. Method for testing porosity of isolating film

Kneading the isolating membrane into a mass, filling the mass into a sample cup, placing the sample cup filled with the sample into a true density tester, sealing a testing system, introducing helium gas according to a program, detecting the gas pressure in a sample chamber and an expansion chamber, and calculating the real volume according to Bohr's law (PV=nRT), thereby obtaining the porosity of the isolating membrane.

TABLE 2

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As can be seen from table 2, the capacity retention rates of the batteries in examples 1 to 54 are superior to those of comparative examples 1 and 2, and the swelling degree of the batteries in examples 1 to 54 is lower than that of the battery containing the capacity compensator in comparative example 2, indicating that the separator provided with the first and second film layers can adsorb oxygen released from the capacity compensator in situ while improving the capacity retention rate of the battery, and reduce the swelling degree of the battery.

As can be seen from examples 1 to 20, by adjusting the volume average particle diameter, the mass ratio of the carbon coating layer, and the thickness of the carbon coating layer of the capacity compensator in the first film layer, the specific discharge capacity and the capacity retention rate of the battery can be improved while the swelling degree of the battery can be reduced.

As can be seen from examples 21 to 47, by adjusting the specific surface area, the porosity, the volume average particle diameter, and the mass ratio of the nanofiller in the second film layer, the specific discharge capacity and the capacity retention ratio of the battery can be improved while the swelling degree of the battery is reduced.

As can be seen from examples 52 and 53, when the base film is included in the separator, the battery can be maintained at a high specific discharge capacity and capacity retention rate while the degree of swelling of the battery is reduced.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the application, and are intended to be included within the scope of the appended claims and description. In particular, the technical features mentioned in the respective embodiments may be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions falling within the scope of the claims.

Claims

1. A separator film, comprising:

a first film layer comprising a first polymer and a capacity compensator comprising a lithium-supplementing agent comprising a lithium-containing metal oxide and/or a sodium-supplementing agent comprising Na ₂ O、Na ₂ O ₂ Or Na (or) ₂ CO ₃ At least one of (a) and (b);

the second film layer is arranged on one side of the first film layer and comprises a second polymer and nano-filler.

2. According to claim 1The isolating film is characterized in that the volume average particle diameter D of the nano filler _v 50 is 5nm-50nm.

3. The barrier film of claim 1, wherein the nanofiller has a mass ratio of 10% -30% based on the total mass of the barrier film.

4. The barrier film of claim 1, wherein the nanofiller comprises at least one of aluminum oxide, silicon dioxide, a metal organic framework-based compound, or a prussian blue analog.

5. The separator according to any one of claims 1-4, wherein at least one of the following conditions is met:

(1) Volume average particle diameter D of the volume compensation agent _v 50 is 50nm-4 μm;

(2) The mass ratio of the capacity compensator is 1.5% -10% based on the total mass of the isolating film.

6. The separator of any one of claims 1-4, wherein the separator has a porosity of 30% -70%.

7. The separator of any of claims 1-4, wherein the thickness of the first film layer is greater than the thickness of the second film layer.

8. The separator of claim 7, wherein at least one of the following conditions is satisfied:

(1) The thickness of the first film layer is 5-30 mu m;

(2) The thickness of the second film layer is 3-15 mu m.

9. The separator according to any one of claims 1 to 4, wherein at least part of the surface of the capacity compensator is formed with a carbon coating.

10. The separator of claim 9, wherein the carbon coating layer has a mass ratio of 2% -10% based on the total mass of the capacity compensator.

11. The separator of any of claims 1-4, further comprising: the base film is arranged on one side, far away from the first film layer, of the second film layer; or (b)

The base film is disposed between the first film layer and the second film layer.

12. The separator of claim 11, wherein at least one of the following conditions is satisfied:

(1) The first polymer comprises at least one of polyolefin polymer, polynitrile polymer or polycarboxylate polymer;

(2) The second polymer comprises at least one of polyolefin polymer, polynitrile polymer or polycarboxylate polymer;

(3) The base film includes a third polymer including at least one of a polyolefin-based polymer, a polynitrile-based polymer, or a polycarboxylate-based polymer.

13. A method of making a separator, comprising:

applying a first slurry comprising a first polymer, a volume compensator, and a first solvent onto a support to form a first film layer;

a second slurry comprising a second polymer, nanofiller, and a second solvent is applied to a side of the first film layer remote from the carrier to form a second film layer.

14. The method according to claim 13, wherein the method further comprises:

applying the first slurry to one side of a base film to form the first film layer, and applying the second slurry to the other side of the base film to form the second film layer; or (b)

The second slurry is applied to a side of a base film to form the second film layer, and the first slurry is applied to a side of the second film layer away from the base film to form the first film layer.

15. The method according to claim 13 or 14, characterized in that the BET specific surface area of the nanofiller is 200m ² /g-1500m ² /g。

16. The method according to claim 13 or 14, wherein the nanofiller has a porosity of 85% -95%.

17. A battery comprising the separator of any one of claims 1-12 or the separator prepared by the method of any one of claims 13-16.

18. The battery of claim 17, wherein the battery further comprises: the positive pole piece and the negative pole piece, the barrier film is located between the positive pole piece and the negative pole piece, the first rete is close to the positive pole piece, the second rete is close to the negative pole piece.

19. A powered device comprising a battery as claimed in claim 17 or 18.